A positional relation when a substrate storage container (front open unified pod, hereinafter suitably referred to as a “FOUP”) has docked with a substrate storage container mounting table is defined by the semiconductor equipment and materials international (SEMI) standard. Due to the molding dimension tolerance of the FOUP and the adjustment error of a load port, a clearance of a maximum of 1 mm is produced between the front surface of a lid of the FOUP and the front surface of an interface part of the substrate storage container mounting table. The air pressure in the FOUP is lower than the air pressure in a clean room. Therefore, if the lid of the FOUP is opened after docking, the polluted clean room atmosphere is brought into the FOUP from the clearance, and airborne particles may adhere to a product substrate and lead to a product failure.